The invention relates to a cutting insert, which has internal coolant delivery, and an assembly using the cutting insert for use in the chipforming removal of material from a workpiece. More specifically, the invention pertains to a cutting insert, as well as an assembly using the cutting insert, used for chipforming material removal operations wherein there is enhanced delivery of coolant adjacent the interface between the cutting insert and the workpiece (i.e., the insert-chip interface) to diminish excessive heat at the insert-chip interface.
In a chipforming material removal operation (e.g., a milling operation, a turning operation, and the like), heat is generated at the interface between the cutting insert and the location where the chip is removed from the workpiece (i.e., the insert-chip interface). It is well-known that excessive heat at the insert-chip interface can negatively impact upon (i.e., reduce or shorten) the useful tool life of the cutting insert. As can be appreciated, a shorter useful tool life increases operating costs and decreases overall production efficiency. Hence, there are readily apparent advantages connected with decreasing the heat at the insert-chip interface.
U.S. Pat. No. 6,053,669 to Lagerberg for CHIP FORMING CUTTING INSERT WITH INTERNAL COOLING discusses the importance of reducing the heat at the insert-chip interface. Lagerberg mentions that when the cutting insert is made from cemented carbide reaches a certain temperature, its resistance to plastic deformation decreases. A decrease in plastic deformation resistance increases the risk for breakage of the cutting insert. U.S. Pat. No. 5,775,854 to Wertheim for METAL CUTTING TOOL points out that a rise in the working temperature leads to a decrease in hardness of the cutting insert. The consequence is an increase in wear of the cutting insert.
Other patent documents disclose various ways to or systems to deliver coolant to the insert-chip interface. For example, U.S. Pat. No. 7,625,157 to Prichard et al. for MILLING CUTTER AND MILLING INSERT WITH COOLANT DELIVERY pertains to a cutting insert that includes a cutting body with a central coolant inlet. The cutting insert further includes a positionable diverter. The diverter has a coolant trough, which diverts coolant to a specific cutting location. U.S. Patent Application Publication No. US 2008-0175678 A1 to Prichard et al. for METAL CUTTING SYSTEM FOR EFFECTIVE COOLANT DELIVERY pertains to a cutting insert that functions in conjunction with a top piece and/or a shim to facilitate delivery of coolant to a cutting location.
U.S. Pat. No. 6,045,300 to Antoun for TOOL HOLDER WITH INTEGRAL COOLANT PASSAGE AND REPLACEABLE NOZZLE discloses using high pressure and high volume delivery of coolant to address heat at the insert-chip interface. U.S. Pat. No. 6,652,200 to Kraemer for a TOOL HOLDER WITH COOLANT SYSTEM discloses grooves between the cutting insert and a top plate. Coolant flows through the grooves to address the heat at the insert-chip interface. U.S. Pat. No. 5,901,623 to Hong for CRYOGENIC MACHINING discloses a coolant delivery system for applying liquid nitrogen to the insert-chip interface.
It is readily apparent that in a chipforming and material removal operation, higher operating temperatures at the insert-chip interface can have a detrimental impact on the useful tool life through premature breakage and/or excessive wear. It would be highly desirable to provide a cutting insert used for chipforming material removal operations wherein there is an improved delivery of coolant to the interface between the cutting insert and the workpiece (i.e., the insert-chip interface), which is the location on the workpiece where the chip is generated). There would be a number of advantages connected with the improved delivery of coolant to the insert-chip interface.
In a chipforming material removal operation, the chip generated from the workpiece can sometimes stick (e.g., through welding) to the surface of the cutting insert. The build up of chip material on the cutting insert in this fashion is an undesirable occurrence that can negatively impact upon the performance of the cutting insert, and hence, the overall material removal operation. It would be highly desirable to provide a cutting insert used for chipforming material removal operations wherein there is enhanced delivery of coolant to the insert-chip interface so as to result in enhanced lubrication at the insert-chip interface. The consequence of enhanced lubrication at the insert-chip interface is a decrease in the tendency of the chip to stick to the cutting insert.
In a chipforming material removal operation, there can occur instances in which the chips do not exit the region of the insert-chip interface when the chip sticks to the cutting insert. When a chip does not exit the region of the insert-chip interface, there is the potential that a chip can be re-cut. It is undesirable for the milling insert to re-cut a chip already removed from the workpiece. A flow of coolant to the insert-chip interface will facilitate the evacuation of chips from the insert-chip interface thereby minimizing the potential that a chip will be re-cut. It would be highly desirable to provide a cutting insert used for chipforming material removal operations wherein there is enhanced delivery of coolant to the insert-chip interface to reduce the potential that a chip will be re-cut. The consequence of enhanced flow of coolant to the insert-chip interface is better evacuation of chips from the vicinity of the interface with a consequent reduction in the potential to re-cut a chip.
A number of factors can impact the extent of the coolant delivered to the insert-chip interface. For example, the size of the structure that conveys the coolant to the cutting insert can be a limiting factor on the extent of coolant supplied to the cutting insert. Thus, it would be highly desirable to provide supply holes that are equal to or larger than the inlets in the cutting insert to maximize the flow of the coolant to the cutting insert. It would be highly desirable to provide a cutting insert in which two or more coolant channels convey coolant to a single discrete cutting location. Further, in order to customize the delivery of coolant, the use of irregular coolant channels and variable areas of the inlet and the discharge in the cutting insert which allow for such customization. One such feature is to provide for a range of diversion angles of the coolant, which can range between about 10 degrees and about 60 degrees
In order to enhance delivery of coolant, it is advantageous to provide for the coolant to enter the cutting insert through the holder. This can include the use of an external coolant supply or an internal coolant supply
In reference to the manufacturing of a cutting insert, there can be advantages in using multiple pieces, which together form the cutting insert. For example, in some instances a cutting insert formed from a base, which presents the cutting edge, and a core can result in enhanced longevity because only the base need to changed after reaching the end of the useful tool life. In such an arrangement, the core is detachably joins to the base whereby the core is re-used when the base wears out. The base and core can join together via co-sintering, brazing and/or gluing. As an alternative, the base and core can contact one another without joining together as an integral member, but remain separate components even though in close contact. In addition, to enhance performance, the base and the core can be from the same or dissimilar materials depending upon the specific application.
When the preferred embodiment of the cutting insert presents a round geometry, certain advantages can exist. For example, when the cutting insert has a round geometry, the assembly of multiple components, e.g., a base and a core, does not need indexing. A round cutting insert is not handed so it can be used in left, right and neutral. In profile turning, up to 50% of the round cutting insert can function as the cutting edge. A round cutting insert is also available to engage an anti-rotation feature.